Simulated Field Temperatures Research Articles

Rising temperature contributed to the outbreak of a macrozooplankton Creseis acicula by enhancing its feeding and assimilation for algal food nearby the coastal Daya Bay Nuclear Power Plant

An outbreak of a macrozooplankton Creseis acicula occurred in the summer of 2020 nearby the Daya Bay Nuclear Power Plant located on the coast of the Daya Bay in the South China Sea. The outbreaks of C. acicula often threaten human health, the marine environment, and other human activities including the safe operation of coastal nuclear power plants. Seawater temperature has been suggested as an important factor influencing such outbreaks. However, the underlying mechanisms through which temperature influences C. acicula remains unknown. Here, we studied the effects of temperature on the ingestion and assimilation of algal food by feeding radiocarbon-labeled algae Chlorella sp. at simulated field temperatures (19–31 °C) to C. acicula collected during the outbreak in the Daya Bay. We also quantified the allocation of the food carbon to dissolved organic carbon (DOC), CO2, and fecal pellets. The results showed that the zooplankton during the same feeding time ingested doubled or tripled algal food at higher temperatures, and it produced and released significantly more DOC, CO2, and fecal pellets with more ingested food carbon. Meanwhile, the assimilation efficiency for the ingested food carbon slightly increased from 48% to 54% with rising temperature. As a result, higher assimilation rates indicating faster growth of C. acicula were observed at higher temperatures. In addition, the high activation energy of 0.908 eV indicated that the assimilation rate was very sensitive to temperature rising. Our results show that relatively rising temperature can enhance C. acicula’s ingestion and assimilation rates for algal food, benefit its growth and metabolism, and contribute to its outbreak. This study provides a mechanistic interpretation for the relationship between rising temperature and the outbreaks of C. acicula and suggests that such outbreaks may occur more frequently and widely in the warming ocean.

Synchrony in the hatching of eggs in the desert locust Schistocerca gregaria (Orthoptera: Acrididae): egg condition influences hatching time in the laboratory and under simulated field temperatures

This study examined the time of hatching of the desert locust Schistocerca gregaria Forskal (Orthoptera: Acrididae) in the laboratory to test the effect of eggs within a pod versus individualized eggs. The pod organization of eggs is thought to play a role in controlling hatching time and to facilitate synchronous hatching at constant temperatures. In the present study, we examined the hatching times of eggs in a pod and individualized eggs under 24-h thermocycles and simulated field temperatures. We tested two patterns of thermocycles consisting of a 12-h thermoperiod (35 or 30 °C) and 12-h cryoperiod (low temperature period; 30 or 25 °C), and two patterns of field temperatures observed in a natural habitat, Mauritania, in May and September. The majority of eggs hatched during low temperature periods in all patterns tested. In addition, the variances of hatching times for individualized eggs were significantly greater than for egg pods in which a clear peak of time of hatching was observed. We show that egg condition influences hatching time under thermocycles of constant and fluctuating temperatures in the laboratory, and may play a role in the adaptive time of hatching.

Comparative seed germination traits in bog and fen mire wetlands

Mires are continental wetlands of high scientific and conservation interest. Knowing the seed germination traits of mire species is essential for understanding their regeneration ecology and conducting active restoration policies. Here, a comparative study of seed germination traits was performed with 34 plant species from bog and fen communities, including many European indicators of these habitats. Freshly collected seeds were exposed to a laboratory germination experiment designed to characterize their response to (1) cold stratification and (2) simulated field temperatures. Germination strategy groups were interpreted according to these responses, and the relation between these groups and different mire types was discussed. Seeds of all tested species had physiological dormancy. Most of them showed conditional type 2 non-deep physiological dormancy: fresh seeds could germinate only at warm temperature, but attained the ability to germinate at colder temperature as they lost dormancy. Most mire species from bogs, poor fens and base-rich fens followed a warm germination strategy analogous to that of other wetland species. Species from this warm group responded to very warm temperatures which rarely occur in the field, and this was interpreted as a gap-detecting mechanism. In contrast, species from calcareous springs and flushes had a cold germination strategy, which would fit with the cold and stable soils where they occur. Finally, a group of species associated with the pioneer Rhynchosporion vegetation of bare peat areas had very low germination, suggesting an intermediate or deep seed dormancy and a long term seed bank.

Comparing phenotypic effects and molecular correlates of developmental, gradual and rapid cold acclimation responses in Drosophila melanogaster

Summary1. To cope with stressful environmental temperatures, organisms can enhance thermotolerance when exposed to sub‐lethal temperatures before thermal stress, a phenomenon referred to as thermal acclimation. Acclimation includes different forms (developmental, gradual or rapid) that vary in ecological importance depending on patterns of diurnal and seasonal thermal variation.2. Here, we complete a comprehensive assessment of how the different forms of acclimation based on simulated field temperatures affect cold tolerance in Drosophila melanogaster under different levels of cold stress (−4·5 °C/2 h and 0 °C/10 h).3. We predict that (i) combinations of acclimation treatments may be particularly beneficial and (ii) benefits of different acclimation types may differ for acute vs. chronic cold stress. We also investigate whether distinct forms of acclimation promote differential molecular responses to stress.4. Acclimation treatments had very large effects on cold tolerance and resulted in phenotypes ranging from sensitive to tolerant individuals within the specific cold stress applied (−4·5 °C/2 h and 0 °C/10 h). Acclimation also influenced expression of several genes (Hsp23, Hsp70, Hsp40, Hsp68, Starvin and Frost) during recovery from cold stress but effects depended on the nature of the acclimation treatment.5. Cumulative effects occurred between different forms of acclimation, and these as well as the different molecular responses point to different underlying mechanisms.6. These results highlight that combined acclimation treatments may strongly impact field stress resistance.

The influence of temperature and presence of predators on growth, survival and energy allocation for reproduction in the Catarina scallop Argopecten ventricosus

Environmental factors are known to modify the life history of marine ectotherms. In a 16-month laboratory experiment, we investigated the influence of temperature and presence of predators on life-history parameters including shell growth, survival and the energy investment in reproduction and body mass of the short-lived (2–3 years) scallop Argopecten ventricosus. In parallel, A. ventricosus was maintained in the field at the Pacific coast of Baja California, México, to compare growth, survival and reproductive effort under natural conditions. For the laboratory treatments, scallops were reared at simulated field temperatures (SFT), 5 °C above SFT and in the presence of predators. Elevated water temperatures caused higher growth and gonad production, although at the cost of increased mortality. Presence of predators induced energy allocation to muscle rather than gonad growth, deferred spawning and extended survival. Field scallops exhibited higher growth, higher reproductive investment and were able to reproduce twice, whereas all laboratory scallops died after the first spawning. The natural variability of environmental parameters such as food and temperature may thus support optimal growth in the field, and when animals are protected from predators, reproduction in the second year of life.

Effect of Variable Temperature on Infection Severity of Podosphaera macularis on Hops

ABSTRACT The effect of variable temperature on the infection severity of Podosphaera macularis was investigated. Potted 'Symphony' hop plants were inoculated and exposed to different temperature regimes that included supraconducive temperatures (30 to 42 degrees C) for varying periods of time (2 to 9 h). Infection severity (lesions per cm(2) of leaf area) was calculated 7 to 10 days after inoculation. Immediately exposing inoculated plants to 30 degrees C for as little as 2 h significantly (P </= 0.05) reduced infection severity compared with exposure at a constant 18 degrees C. However, exposure of inoculated plants to optimal conditions for 24 or 48 h prior to exposure to supraconducive conditions reduced this effect for plants exposed to 30, 33, or 36 degrees C. Exposure to 39 or 42 degrees C for 2 or more hours resulted in infection frequencies not significantly different from that of the uninoculated control regardless of prior exposure to favorable conditions. Exposure to simulated field temperatures programmed into growth chambers indicated that inoculation at 1700 or 2100 h resulted in significantly more disease than did inoculation at 0900 or 1300 h. Plants exposed to supraconducive or simulated field temperatures for 7 days prior to inoculation developed significantly lower disease severity than did plants maintained at 18 degrees C for 7 days. The magnitude, length, and time of exposure to supraconducive temperatures in relation to time of inoculation plays an important role in the development of hop powdery mildew, and rules addressing these variables could be a useful addition to disease risk assessment models.

Mortality Induced by Bacillus popilliae in Cyclocephala parallela (Coleoptera: Scarabaeidae) Held under Simulated Field Temperatures

The bacterium, Bacillus popilliae Dutky, causes milky disease in numerous species of scarabs around the world. Bacillus popilliae induced mortality in naturally infected grubs (third instars) of Cyclocephala parallela Casey was measured when held under simulated field temperatures. Our data show that visual examination in the field underestimates the percentage of grubs actually infected by B. popilliae. 5.6 to 8.2 times as many milky disease infected grubs died during the first 60 days of incubation under simulated field temperatures than did uninfected grubs. These data show that the widely used prevalence value underestimates the total mortality which this bacterium ultimately causes to C. parallela.

Embryogenesis of Dinocras cephalotes, Perla grandis and P. marginata (Plecoptera: Perlidae) in different temperature regimes

1. Temperature dependence of embryogenesis of the three perlid stoneflies Dinocras cephalots, Perla grandis and P. marginata was investigated by means of incubation experiments. Special emphasis was laid on the effect of fluctuating temperatures and on intraspecific differences between populations from two different field sites in the Swiss prealps (i.e. River Necker and River Thur).2. Dinocras cephalotes embryos develop between 6.3 and 26.6 °C. The lower threshold temperature is lower than has been reported for more northern populations (i.e. from England and Norway), indicating the existence of a latitudinal gradient. Perla grandis eggs only developed between 9.9 and 18.4 °C. In P. marginata, successful embryogenesis was observed between 9.9 and 18.4 °C, but not enough eggs were available to explore the threshold temperatures.3. Embryogenesis of D. cephalotes and P. grandis was significantly faster at a 12/16 °C daily fluctuating temperature regime than at a constant 14 °C. However, no significant difference was found between the development under simulated field temperature regimes (with less distinct daily amplitudes) and constant temperatures.4. D. cephalotes, hatching of eggs from the Necker population was much less synchronous than that in the Thur population. Since the Necker discharge regime is harsher than the Thur regime, it is possible that this asynchrony spreads the risk of destruction during bed‐moving floods.

Measurement of monoterpene hydrocarbon levels in vapor phase surrounding single-leaf pinyon (Pinus monophylla Torr. &amp; Frem.: Pinaceae) understory litter

A headspace air-sampling experiment was performed in the laboratory to determine the identity and concentrations of monoterpene hydrocarbons that could be attained in the vapor phase surrounding single-leaf pinyon pine (Pinus monophylla Torr. & Frem.) understory litter using controlled air collection conditions at a simulated field temperature of 37.8°C. The total monoterpene hydrocarbon content in 21 sequential samples of air collected from a sealed glass carboy packed with 1.44 kg of single-leaf pinyon litter equivalent to a bulk density of 0.15 g/cm(3) averaged 3.56 ± 1.04 mg/liter. The monoterpenesα-pinene and camphene were present in the vapor phase at the highest concentrations, averaging 2.40±0.64 and 0.68±0.22 mg/ liter, respectively. Myrcene,β-pinene, 3-carene,β-phellandrene, andγ-terpinene were all present at average concentrations below 0.30 mg/liter. The first two traps of the sequential air samples yielded the highest concentrations for the monoterpene hydrocarbons; however, the average total levels were relatively stable throughout the remaining 19 traps. Therefore, the data indicate that these hydrocarbons volatilize from the source pinyon litter and maintain an equilibrium in the vapor phase. Although this analysis was conducted using an artificial system, combined with results from our previous studies, mounting evidence indicates that monoterpene hydrocarbons present in the vapor phase of the single-leaf pinyon understory may be toxic to a variety of native plant species and thus further implicates allelopathy as a significant contributor to the observed patterning of associated vegetation in these forests.

INCIDENCE OF BACILLUS POPILLIAE IN DIFFERENT LIFE STAGES OF FLORIDA SUGARCANE GRUBS (COLEOPTERA: SCARABAEIDAE)

All life stages of Cyclocephala parallela Casey and Ligyrus subtropicus Blatchley were collected from commercial sugarcane fields in southern Florida from May, 1985 to May, 1988. These specimens were examined using phase contrast microscopy for the presence of the milky disease bacteria, Bacillus popilliae Dutky. In addition, field soil temperatures were measured, and the survival of milky grubs under simulated field temperatures was determined in a laboratoiy. Bacillus popilliae was not detected in the eggs or pupae of either grub species. The bacterium was found in 0.2% and 0.3% of adults in C. parallela and L. subtropicus respectively. The highest incidence of B. popilliae in both species was observed in the larval stage being 6.1% and 1.9% in C. parallela and L. subtropicus respectively. Survival data showed that B. popilliae was not limited in its development in infected third instar grubs by soil temperatures at any time during the year in Florida sugarcane fields.

Effects of Simulated Field Temperatures and Chilling on Itchgrass (Rottboellia exaltata), Corn (Zea mays), and Soybean (Glycine max)

Mathematical growth analysis techniques were used to study the effects of simulated field temperatures and chilling events on the growth of the exotic noxious weed itchgrass (Rottboellia exaltataL. f.) and adapted varieties of corn (Zea maysL. ‘DeKalb XL43’ and ‘DeKalb XL395′), and soybean [Glycine max(L.) Merr. ‘Corsoy’, ‘Williams', and ‘Tracy’] in climate-controlled greenhouses and growth chambers. Itchgrass grew vigorously and produced seed in temperature regimes simulating the warmest 4 months of the growing season in the Gulf Coast states (30/25 C, day/night), the central Midwest (27/21 C), and the northern Midwest (23/18 C). At 30/25 C day/night, itchgrass produced 707 g of dry matter and 1907 seed per plant after 119 days. Itchgrass produced 621 g dry matter and 1429 seed at 27/21 C and 499 g dry matter and 1160 seed at 23/18 C. Itchgrass and adapted varieties of corn and/or soybeans were grown in four additional temperature regimes simulating the first 5 weeks of the growing seasons for corn and soybean at Madison, Wisconsin (19/11 C day/night); for soybean at Carbondale, Illinois (24/20 C); for corn at Waycross, Georgia (20/14 C); and for soybean at Baton Rouge, Louisiana (27/23 C). After 24 days of growth, half the plants in each regime were exposed to 3 days of chilling (11/4 C for Madison, 17/10 C for Carbondale, 15/6 C for Waycross, and 24/18 C for Baton Rouge) and returned to the original growth regimes for recovery. The chilling treatments reduced dry matter production, net assimilation rate, and leaf area duration more in itchgrass than in corn or soybean. After recovery, the previously chilled itchgrass plants had greater reductions in height, leaf area, and dry weight, compared to unchilled controls, than did corn or soybean. Weed/crop ratios in height, leaf area, and dry weight for itchgrass/corn were significantly reduced by chilling. In the two cooler regimes, weed/crop ratios in leaf area and dry weight for itchgrass/soybean were significantly reduced by chilling. Because of its sensitivity to cool temperatures, itchgrass, is unlikely to be an important early-season competitor with corn or with soybean outside the South.

Development, longevity and fecundity ofChelonus blackburni [Hym.: Braconidae] as a parasite ofPectinophora gossypiella [Lep.: Gelechiidae

Development, longevity, and fecundity ofChelonus blackburniCameron, a uniparental egg-larval parasite of pink bollworm,Pectinophora gossypiella (Saunders), was studied in the laboratory. The habits of and brief descriptions for the egg and larval stages are given. Developmental times decreased with increasing temperature within a range of 20°–32.2°C; a minimum of 22 days was required for development from egg to adult. At a simulated field temperature regimen, longevity averaged 11.6 days, and the mean fecundity was 909 eggs per female.